全文获取类型
收费全文 | 4506篇 |
免费 | 314篇 |
国内免费 | 2篇 |
出版年
2022年 | 31篇 |
2021年 | 66篇 |
2020年 | 36篇 |
2019年 | 57篇 |
2018年 | 82篇 |
2017年 | 63篇 |
2016年 | 95篇 |
2015年 | 178篇 |
2014年 | 201篇 |
2013年 | 244篇 |
2012年 | 307篇 |
2011年 | 341篇 |
2010年 | 186篇 |
2009年 | 156篇 |
2008年 | 253篇 |
2007年 | 245篇 |
2006年 | 254篇 |
2005年 | 215篇 |
2004年 | 210篇 |
2003年 | 191篇 |
2002年 | 178篇 |
2001年 | 120篇 |
2000年 | 106篇 |
1999年 | 103篇 |
1998年 | 64篇 |
1997年 | 45篇 |
1996年 | 45篇 |
1995年 | 44篇 |
1994年 | 21篇 |
1993年 | 29篇 |
1992年 | 74篇 |
1991年 | 49篇 |
1990年 | 43篇 |
1989年 | 50篇 |
1988年 | 36篇 |
1987年 | 45篇 |
1986年 | 38篇 |
1985年 | 51篇 |
1984年 | 33篇 |
1983年 | 27篇 |
1982年 | 16篇 |
1981年 | 16篇 |
1980年 | 12篇 |
1979年 | 23篇 |
1976年 | 12篇 |
1975年 | 14篇 |
1974年 | 13篇 |
1973年 | 11篇 |
1972年 | 13篇 |
1971年 | 12篇 |
排序方式: 共有4822条查询结果,搜索用时 187 毫秒
961.
Plants protect their roots by alerting the enemies of grubs 总被引:7,自引:0,他引:7
Rob W.H.M. van Tol Anton T.C. van der Sommen Mari I.C. Boff Jan van Bezooijen Maurice W. Sabelis & Peter H. Smits 《Ecology letters》2001,4(4):292-294
Plant roots in the soil are under attack from many soil organisms. Although many ecologists are aware of the presence and importance of natural enemies in the soil that protect the plants from herbivores, the existence and nature of tritrophic interactions are poorly understood. So far, attention has focused on how plants protect their above-ground parts against herbivorous arthropods, either directly or indirectly (i.e. by getting help from the herbivore's enemies). This article is the first in showing that indirect plant defences also operate underground. We show that the roots of a coniferous plant ( Thuja occidentalis ) release chemicals upon attack by weevil larvae ( Otiorhynchus sulcatus ) and that these chemicals thereby attract parasitic nematodes ( Heterorhabditis megidis ). 相似文献
962.
T. Motoyama Makoto Fujiwara Nobuko Kojima Hiroyuki Horiuchi Akinori Ohta M. Takagi 《Molecular & general genetics : MGG》1997,253(4):520-528
We previously isolated three chitin synthase genes (chsA, chsB, and chsC) from Aspergillus nidulans. In the present work, we describe the isolation and characterization of another chitin synthase gene, named chsD, from A. nidulans. Its deduced amino acid sequence shows 56.7% and 55.9% amino acid identity, respectively, with Cal1 of Saccharomyces cerevisiae and Chs3 of Candida albicans. Disruption of chsD caused no defect in cell growth or morphology during the asexual cycle and caused no decrease in chitin content in hyphae.
However, double disruption of chsA and chsD caused a remarkable decrease in the efficiency of conidia formation, while double disruption of chsC and chsD caused no defect. Thus it appears that chsA and chsD serve redundant functions in conidia formation. 相似文献
963.
Germline transformation of the silkworm Bombyx mori L. using a piggyBac transposon-derived vector 总被引:21,自引:0,他引:21
Tamura T Thibert C Royer C Kanda T Abraham E Kamba M Komoto N Thomas JL Mauchamp B Chavancy G Shirk P Fraser M Prudhomme JC Couble P Toshiki T Chantal T Corinne R Toshio K Eappen A Mari K Natuo K Jean-Luc T Bernard M Gérard C Paul S Malcolm F Jean-Claude P Pierre C 《Nature biotechnology》2000,18(1):81-84
We have developed a system for stable germline transformation in the silkworm Bombyx mori L. using piggyBac, a transposon discovered in the lepidopteran Trichoplusia ni. The transformation constructs consist of the piggyBac inverted terminal repeats flanking a fusion of the B. mori cytoplasmic actin gene BmA3 promoter and the green fluorescent protein (GFP). A nonautonomous helper plasmid encodes the piggyBac transposase. The reporter gene construct was coinjected into preblastoderm eggs of two strains of B. mori. Approximately 2% of the individuals in the G1 broods expressed GFP. DNA analyses of GFP-positive G1 silkworms revealed that multiple independent insertions occurred frequently. The transgene was stably transferred to the next generation through normal Mendelian inheritance. The presence of the inverted terminal repeats of piggyBac and the characteristic TTAA sequence at the borders of all the analyzed inserts confirmed that transformation resulted from precise transposition events. This efficient method of stable gene transfer in a lepidopteran insect opens the way for promising basic research and biotechnological applications. 相似文献
964.
Shinji Masuda Rei Ikeda Tatsuru Masuda Haruki Hashimoto Tohru Tsuchiya Hiroko Kojima Jiro Nomata Yuichi Fujita Mamoru Mimuro Hiroyuki Ohta Ken‐ichiro Takamiya 《The Plant journal : for cell and molecular biology》2009,58(6):952-960
In angiosperms, chlorophyll biosynthesis is light dependent. A key factor in this process is protochlorophyllide oxidoreductase (POR), which requires light to catalyze the reduction of protochlorophyllide to chlorophyllide. It is believed that this protein originated from an ancient cyanobacterial enzyme that was introduced into proto‐plant cells during the primary symbiosis. Here we report that PORs from the cyanobacteria Gloeobacter violaceus PCC7421 and Synechocystis sp. PCC6803 function in plastids. First, we found that the G. violaceus POR shows a higher affinity to its substrate protochlorophyllide than the Synechocystis POR but a similar affinity to plant PORs. Secondly, the reduced size of prolamellar bodies caused by a knockdown mutation of one of the POR genes, PORA, in Arabidopsis could be complemented by heterologous expression of the cyanobacterial PORs. Photoactive protochlorophyllide in the etioplasts of the complementing lines, however, was retained at a low level as in the parent PORA knockdown mutant, indicating that the observed formation of prolamellar bodies was irrelevant to the assembly of photoactive protochlorophyllide. This work reveals a new view on the formation of prolamellar bodies and provides new clues about the function of POR in the etioplast–chloroplast transition. 相似文献
965.
Atsushi Sato Nobuo Ida Mari Ishikawa Kazuhiro Tanahashi Haruji Nakamura Yukihiko Sho Terukatsu Arima Tetsunosuke Kunitomo 《Microbiology and immunology》1993,37(4):295-304
An enzyme-linked immunosorbent assay (ELISA) was developed for the detection of anti-HCV antibody. We assayed for antibodies against either oligopeptide (S29-1) deduced from the nucleocapsid gene or the product of nonstructural region (NS3) synthesized in a recombinant Escherichia coli (S4). To reduce false-positive results induced by non-specific binding of antibodies with a carrier protein and to increase the sensitivity of an immunoassay, non-fused S4 peptide was prepared by the recombinant DNA technique and site-specific proteolysis (by factor Xa). In 71 non-A, non-B hepatitis patients with chronic liver disease, 70 (98.5%) were positive by S29-1/S4 ELISA as well as by a second-generation test (Abbott II). On the other hand, of 40 serum samples from blood donors, in which anti-N14 (core) and C100-3 antibodies were not detected but hepatitis C virus (HCV) RNA was detectable by polymerase chain reaction (PCR), 24 (60%) were positive by S29-1/S4 ELISA, whereas only 18 (45%) were diagnosed by Abbott II. In addition, based on results in a small group of 92 blood donors, detection of anti-S29-1/S4 antibody correlated well with HCV viremia as confirmed by PCR. These results indicated that the preparation of non-fused protein (S4) by recombinant DNA technique and a combination of S29-1 and S4 as immobilized antigens in an ELISA provide a sensitive and specific diagnosis for HCV infection with good correlation with the presence of viral RNA as confirmed by PCR. 相似文献
966.
967.
968.
969.
De Sousa Paulo Cesar Alves Souza Stênio Steferson Silva E. Meira Filipe Sathler Meira Rennan De Oliveira Gomes Hugo Teixeira Silva-Cardoso Inaê Mariê De Araújo Scherwinski-Pereira Jonny Everson 《In vitro cellular & developmental biology. Plant》2020,56(5):618-633
In Vitro Cellular & Developmental Biology - Plant - An efficient protocol is reported for in vitro plant regeneration through somatic embryogenesis in Piper aduncum, a Brazilian Amazon species... 相似文献
970.